When is used to treat cancer, particularly tumors, it is critical to protect surrounding healthy tissue from the radiation to the extent possible. This is often accomplished by shielding the patient from the radiation source with lead alloy plates or shields having irregularly shaped openings which simulates precisely the size and shape of the tumor so that the only radiation permitted through the shield falls on the tumor. The lead alloy shield thus protects healthy tissue around the treated area. These shields are custom cast for each individual based on the size, shape and location of the tumor. The shields are individually cast using a molding process employing a low melting temperature alloy. A pattern of styrofoam is cut into the tumor shape. This pattern is then placed in the mold, and the molten metal is poured around it. The metal is then permitted to cool and harden to form the shield.
One of the unique characteristics of the low temperature alloy is that it expands slightly as it solidifies. Therefore, it is difficult to remove the casting, once cooled, from a fixed mold due to this expansion.
Due to the extreme importance of radiation therapy shields, a need exists for a method and mechanism that eliminates the problems associated with the casting process, including the difficulty of removing castings from the mold.